On Sun, 24 Dec 2023 09:45:39 -0800 (PST), three_jeeps
<snip
Post by three_jeepsPost by leggI've seen LCDs that have obvious damage/discoloration
and flakey elements before, but never something that
was permanently, uniformly dark.
There's no carbon press strip to degrade, just 15
solderable in-line pins.
I would suspect the controller chip, or its ceramic
resonator, but the chip seems to be performing normally.
The unit runs.
"All necessary wiggles being delivered to solderable pins" -
All the LCD segment lines change state appropriately?
Checked voltages on all segment pins at the same time
(with perhaps a 16 line digital analyzer)?
dream on
Post by three_jeepsBias voltage on the LCD correct? If all true then the LCD is dead.
Does this model have a separate LCD controller chip or does it use a micro with a number of DIO lines?
Service manual shows 4x9 connections more suited to an LED display
coming from a 64pin micro through a quad buffer and nine unbuffered
lines from paralleled ports with 100R series limiters.
The current rev board is a 56pin QFN package driving the 15 pins of
the display directly.
3 of the 15 pins generate quad-state ~ramps between 0 and 5V.
Pins 1 , 2 and 10.
The rest just clock (150Hz) between the two mid-state levels, in
sync with the ~ramping steps.
This controls segments of 4 digit clock, its middle colon and
5 symbols for mode of operation, spaced ~ equally below the digits
and mid-colon.
I've searched all over for a more accurate service manual, or
a revision that includes the change to micro and display, but
this is only reflected in purchasing spares. The old control
panel assy number is retired to be replaced by . . .
A custom LCD-only part for the control board assembly isn't a
likely after-market item. The whole panel is available for $$$.
This one is from 2012, about half way through the product's history.
RL